This invention relates to a multi-layer seal member for use in sealing joints between components which are subject to high temperature. In particular it finds application where the components are of dissimilar materials such as ceramics or ceramic composites and metals.
Ceramics and ceramic composite materials are often employed for the manufacture of components which are subject to high temperatures. When such components have to be joined to other components made of metal, for example in the exhaust ducting of a gas turbine engine, sealing between the components is a problem. Over a wide temperature range differential expansion and contraction characteristics of the different materials reduces seal efficiency due to relative movement of the components. For instance, in the example mentioned, seals have to be capable of operating satisfactorily at temperatures in excess of 1000.degree. C. to prevent the leakage of exhaust gas from the ducting.
Known sealing mediums in present use include ceramic fibers compressed into annular rings, or O-rings, of circular cross-section and impregnated with a binding agent. These known sealing means suffer from certain disadvantages such as, for example, the inability to respond quickly to the dimensional changes which take place as the components of a joint react to temperature change. The selection of a seal member especially with reference to its thermal conductivity is thus particularly important since it determines the maximum operating temperature of a sealed joint.
The invention has for an objective to provide an improved seal member for abutting components subject to temperature change.
Another objective of the invention is to provide an improved seal member such as an O-ring for sealing abutting surfaces of dissimilar materials such as ceramic and metal subject to relative movement due to differential thermal expansion. The surfaces may be planar surfaces, for example, end flanges or the surfaces of telescopically arranged cylindrical members.
A further objective of the invention is to provide an improved seal member such as an O-ring which tightens as temperature increases.
These and further objectives will be apparent from the following description.